1. Field of the Invention
This invention relates to access control for digital video stream data, such as so-called video elementary stream data. In addition to the video stream data, the invention may optionally be used in respect of at least one of audio content, metadata content, text content, image content and so on, for example audio/visual content.
2. Description of the Prior Art
The growth of new digital infrastructures, including digital devices and high-speed networks, combined with increasing processor power is making video content creation, manipulation and distribution both simpler and faster. While this greatly aids legitimate usage of the content, a disadvantage is that unauthorised abuse of such content (particularly copyright content), such as unauthorised reproduction or distribution, is also becoming easier and more damaging to the content owner.
The situation is made more complicated in that commercial considerations may require the content owner to allow a potential customer to see or use the content in a trial situation before committing to purchase rights to use the content from the owner.
So-called digital rights management (DRM) systems have been proposed, in order to try to address these problems. Known DRM systems generally use a form of data encryption to encrypt content for distribution. An authorised recipient is supplied with a decryption key to allow the recipient to decrypt the encrypted content.